FALSE-SCORPIONS 103 



to prefer a rough surface to walk on. Thanks to the aroHum, a 

 trumpet- shaped membranous sucker beneath the claws of the 

 walking legs, false-scorpions are able to climb vertically and walk 

 upside-down on the under surfaces of stones and logs. If they 

 should happen to fall on their backs, however, they can only right 

 themselves with difficulty by arching their bodies and rocking 

 from side to side, or by grasping some nearby object with their 

 claws. 



The phenomenon of the utilisation of another animal for trans- 

 port, to which the name 'phoresy' is commonly applied, is perhaps 

 a particular type of commensalism. An example is afforded by 

 Limosina sacra, a Borborid fly, numbers of which constantly ride 

 on the backs of dung beetles in North Africa, apparently for the 

 purpose of ovipositing in the particularly choice assemblage of 

 faecal matter that the beetles collect and consolidate. In a similar 

 way, bird-lice (Mallophaga) are frequently conveyed from one 

 host to another by the Hippoboscid fly Ornithomyia avicularia. 

 About twenty-five species of pseudoscorpion are known to obtain 

 transport from one place to another on other animals such as 

 Diptera, Hymenoptera, Coleoptera, Hemiptera, Orthoptera and 

 other insects, harvest-spiders and birds. Beier (1948) provides a 

 useful summary of the extensive literature not only on phoresy 

 but also on other types of association in which false-scorpions are. 

 concerned. He lists the species that have been found inhabiting 

 the nests of birds and mammals, termites, ants and other Hymen- 

 optera, and tabulates the Chernetes that have been recorded as 

 attached to the extremities of the limbs and to the bodies of insects 

 and other arthropods. The most important phoretic species in 

 Europe is Lamprochernes nodosus which is not infrequently found 

 attached to the legs of houseflies in summer and autumn although 

 it also clings to hover-flies and other insects. False-scorpions oc- 

 casionally ride on the backs of beetles, sheltering under their 

 elytra. Cordylochernes scorpioides is a well-known example fre- 

 quently phoretic on the beetle Acrocinus longimanus in tropical 

 America. 



Various explanations of the phoretic habit have been suggested, 

 but in most cases it seems that this behaviour is either accidental 

 or motivated by hunger. Only female false-scorpions are phoretic, 



